Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
H,W=map(int, input().split())
S = tuple(input().rstrip() for _ in range(H))
a=0
d=[(1,0),(-1,0),(0,1),(0,-1)]
lity=[[0 for i in range(W)] for j in range(H)]
lity[0][0]=1
def roop()->None:
  p=[(0,0)]
  while p:
    x,y=p.pop(0)
    for dx,dy in d:
      if 0<=x+dx<H and 0<=y+dy<W and S[x+dx][y+dy]=='.' and lity[x+dx][y+dy]==0:
        p.append((x+dx,y+dy))
        lity[x+dx][y+dy]=lity[x][y]+1
roop()
white=sum(t.count(".") for t in S)
x=lity[-1][-1]
ans = white - x
if 0<x:
  print(ans)
else:
  print(-1)